1. Field of the Invention
The present invention relates to a picture processing apparatus and a picture processing method that are suitable for a television receiver that performs both a multiple-picture display of which a plurality of pictures are displayed in a row on a background screen and a reduced picture display of which a reduced picture is displayed along with an on-screen picture such as text.
2. Description of the Related Art
A television receivers that can perform both a multiple-picture display of which a plurality of pictures are displayed in a row on a background screen and a reduced picture display of which a reduced picture is displayed along with an on-screen picture such as text. FIG. 1 shows an example of a displaying apparatus of such a television receiver.
In FIG. 1, a plurality of video signals are input from input terminals 102A, 102B, and so forth to an input signal selecting portion 101. The input signal selecting portion 101 selects two video signals of two sources that are displayed on the screen from the video signals that are input from the input terminals 102A, 102B, and so forth.
The selected two video signals of two sources are supplied to A/D converters 103A and 103B. The A/D converters 103A and 103B digitize two video signals of two sources that have been selected by the input signal selecting portion 101. The two video signals of two sources that have been digitized by the A/D converters 103A and 103B are supplied to a picture processing portion 104.
The picture processing portion 104 performs a multiple-picture displaying process and a reduced picture displaying process. To accomplish such processes, the picture processing portion 104 has a picture memory 105.
When two pictures are displayed, the two video signals of two sources are written to the picture memory 105. At desired timings, the two video signals of two sources are read from the picture memory 105 and displayed on the background screen. At that point, the two video signals of two sources are thinned out or interpolated so as to adjust the picture sizes.
Output signals of the picture processing portion 104 are supplied to a D/A converter 106. The D/A converter 106 converts the output signals of the picture processing portion 104 into analog signals. Output signals of the D/A converter 106 are supplied to a CRT display 107.
Video signals supplied to the input terminals 102A, 102B, and so forth may for example letter box signals or side panel signals that contain non-picture portions.
There are three types of formats of video signals. The three types of video signals differ in the number of effective pixels. The number of effective pixels of the first type is (720×480). The number of effective pixels of the second type is (1280×720). The number of effective pixels of the third type is (1920×1080).
In the first format of which the number of effective pixels is (720×480), the angle of view is (4:3) that is a standard screen. In the second format of which the number of effective pixels is (1280×720) and the third format of which the number of effective pixels is (1920×1080), the angle of view is (16:9) that is a wide screen.
As shown in FIG. 2A, when the angle of view is 16:9 and the aspect ratio of the effective picture area is 4:3, black non-picture portions are added to the left and right of the picture so that the angle of view becomes 16:9. Such a signal is referred to as side panel signal.
In addition, as shown in FIG. 2B, when the angle of view is 4:3 and the aspect ratio of the effective picture area is 16:9, black non-picture portions are added to the top and bottom of the picture so that the angle of view becomes 4:3. Such a signal is referred to as letter box signal.
Thus, as shown in FIG. 2A, a side panel signal has non-picture portions on the left and right of the picture. On the other hand, as shown in FIG. 2B, a letter box signal has non-picture portions at the top and bottom of the picture. Thus, as was described above, when an input video signal is written to the picture memory 105 and read therefrom at a proper timing corresponding to the screen position in a predetermined picture size, if the input video signal is a letter box signal or a side panel signal, the non-picture portions are also processed. Thus, when a multiple-picture displaying process is performed, the picture of the side panel signal or letter box signal becomes small. On the other hand, when the reduced picture displaying process is performed, the display area on the screen cannot be effectively used.
FIGS. 3A, 3B, and 3C show an example of which two pictures are displayed with a picture of a side panel signal and a picture of a full line signal.
As shown in FIG. 3A, all the picture of a side panel signal S101 that contains left and right non-picture portions is written to the picture memory. The picture size of the video signal written to the picture memory is adjusted in the size of all the picture. On the other hand, as shown in FIG. 3B, a full line signal S102 is written to the picture memory. The picture size of all the picture of the video signal is adjusted in the picture memory. The adjusted picture is read from the picture memory and displayed on the background screen. As a result, as shown in FIG. 3C, two pictures that are a picture G101 formed with the side panel signal S101 and a picture G102 formed with the full line signal S102 are displayed. As shown in FIGS. 3A and 3B, the aspect ratio of the effective picture area of each of the two signals S101 and S102 is (4:3). Thus, the pictures will be displayed in the same size. However, as shown in FIG. 3C, when the two pictures G101 and G102 are displayed in a row, due to the left and right non-picture portions, the picture G101 formed with the side panel signal S101 becomes smaller than the picture G102 formed with the full line signal S102.
FIGS. 4A and 4B show an example of which the area of a picture of a side panel signal S111 is reduced on the display screen. As shown in FIG. 4A, all the picture of the side panel signal S111 that contains the left and right non-picture portions is written to the picture memory. The picture size of the video signal written to the picture memory is adjusted in the size of all the picture. The adjusted picture is read from the picture memory and displayed on the background screen. As shown in FIG. 4B, in addition to a picture G111 formed with the side panel signal S111, an on-screen picture G112 such as text is displayed.
In this case, since the picture of the side panel signal S111 contains the left and right non-picture portions, The reduced picture G111 has a wasteful portion. Due to the wasteful portion, the area for the on-screen display picture G112 such as text becomes small. Consequently, the utilization efficiency of the screen becomes low.